http://www.420magazine.com/forums/grow-supply-product-reviews/108192-truth-about-magnetic-ballasts-power-wastage.html
I came upon that, its a good read and interesting. The basics of it are he hooked up 2 400w's and 1 150w and checked it with an energy usage meter and it only came out to 962 watts. That means the ballasts(3 of them) were only sucking down 12 watts combined to power 950 watt of lights.(962 watts went in, 950 went out, in case anyone doesn't see that) How much more efficient can you get than that? Its only something like 5 watts being lost to the 400w magnetic ballast. Ill put some bullet points from it. Keep in mind, I didn't do these tests, and I'm just posting the information.
- a 400w hps magnetic ballast uses about 5 watts more than it outputs at normal operation.
- Digital Ballasts may be rated more efficient by calculating the 'spike' of energy needed to start a bulb by the magnetic ballast.
- 5 watts an hour x 12 = 60 x 30 = 1800. 1800 watts = 1.8 kw, 1.8 kw is something like 20 cents where I live, more or less. That would be the monthly savings for a digital in flowering according to those numbers.
- Someone suggested that the reason digital ballasts run cooler are because they are a huge aluminum heatsink, whereas magnetic ballasts have absolutely no heatsink in most cases. They went further to say this could be the only reason they are cooler, and not due to efficiency.
- The reason most magnetic ballasts are loud is because your enclosure is cheap or the screws are loose or other issues not really due to it being magnetic.
The energy usage thing surprised me, but I already assumed the other things. I am going to get a lumen tester and a kill-a-watt and see how many watts my new 600 and my 400 use. My new 600, since its in a large commercial case actually makes less noise.
If digitals don't get hot, why do they have exhaust fans built in? Wouldn't putting an exhaust fan in the case of a magnetic ballast make it run very much cooler? Or alternatively a foot long aluminum heatsink on it like the lumateks?
On another note, switching from 400w hps to 600w hps with aircooled hood only raised the temps by 1 degree in my 2x4 with 1 modded stanley blower operating it.